1. Field of the Invention
The present invention relates to an image communication apparatus having a memory for storing received image data.
2. Related Background Art
There are known facsimile apparatus of the type which uses as a recording apparatus a so-called page printer such as a laser beam printer whose recording operation is controlled in units of one page of image data. A page printer uses one page as its minimum data recording unit, the recording processing time for one line is nearly constant, and the recording operation cannot be stopped in the midst of recording one page.
Such a page printer is generally provided with a buffer memory for storing one page of image data, which is the minimum unit to be processed at a time. The buffer memory is provided because the time required for obtaining one page of image data during facsimile communication fluctuates.
If an image to be copied is read and recorded with complete synchronization between reading and recording, such a buffer memory is not necessary. However, such synchronization is not usually ensured, but image data is recorded after one page of image data is completely stored. Such a buffer memory has not been used as an image memory for storing image data of one unit of communication.
The reason for this is to allow receiving one image and simultaneously copying an original using the printer, even if image data to be transmitted is being stored in an image memory.
A page buffer used for a page printer of a facsimile apparatus is required to store typically a one page original of A4 size, the capacity thereof being relatively large. For instance, the memory capacity of about 500 k Bytes is required for storing a single A4 original binarized at a resolution of 8 pixels/mm.
The page buffer is used, however, only for recording data with a printer as described before, resulting in a poor memory efficiency.
Facsimile apparatus using such a page printer are disclosed in U.S. Pat. Nos. 4,677,649; 4,712,139; 4,679,093; 4,631,596; 4,717,967; 4,885,641; 4,827,349; 4,910,785; and 4,727,276; 4,907,094; and 4,922,349.
There is also known an apparatus which performs so-called reception-by-memory, namely, when the recording unit cannot be operated due to a deficiency of recording material such as recording paper and toner, received image data is temporarily stored in an image memory and outputted when the operation of the recording unit is recovered. Even if the recording unit cannot be operated, such an apparatus uses a page buffer for a printer and an image memory independently of each other. Therefore, the page buffer for a printer remains unused and empty until operability is recovered.
Facsimile apparatus performing reception-by-memory are disclosed in U.S. Pat. Nos. 4,717,967 and 4,789,900; and in U.S. patent applications Ser. Nos. 250,099 (filed on Sep. 28, 1988) and 446,479 (filed on Dec. 5, 1989).
Facsimile apparatus solving the above-described problems have not been proposed as yet.